Dr. goodrich wanted to demonstrate that his tires were better than those of his competitor dr. goodyear. from car registration and leasing records, he found 40 salesmen who drove the same model of automobile approximately the same number of miles per week. anonymously, dr. goodrich hired an independent research assistant, who was unaware of the purpose of the study, to randomly assign 20 of the salesmen a new set of unmarked goodrich radials, and the other 20, a new set of unmarked goodyear radials of the same price and quality. after six months and an average of 15,000 miles traveled by both groups the assistant arranged for the salesmen to exchange tires. after another six months, and similar mileage, the assistant measured the amount of tread wear and reported the goodrich tires had actually worn more than the goodyear tires. accordingly, dr. goodrich was forced to drop his commercials claiming to have better tires than the "other guy." are the researcher's conclusions warranted (yes/no/maybe)? name the independent variable(s): name the dependent variable(s): name the confounded variable(s): what method(s) would "unconfound" the experiment? what method(s) would improve internal validity of findings?